Tilapia Topic, Disease Treatment,

Formalin/Malachite Green

Information about Formalin/Malachite Green Treatment

Formalin/malachite green is used for control of Ichthyophthirius. The treatment is applied as an prolonged bath at a dosage of 0.1 ppm malachite green and 24 ppm formalin. In usual circumstances the treatment is applied on alternate days for three or more applications.

Malachite green is not cleared for use in food fish and although certain commercial formulations of formalin are approved for use in food fish formalin is not specifically approved for use with tilapia. Both formalin and malachite green are considered to be a potential carcinogens. Thus, formalin/malachite green should not be used as a treatment for tilapia for eventual human consumption. In addition, avoid direct contact with formalin or malachite green and do not inhale formalin vapors. Thus, preparation of a working solution for treatment of fish should be done in an area that is well ventilated or a respirator should be worn.

Many species of fish are sensitive to malachite green and do not tolerate treatment well. Also, very young tilapia may be sensitive to malachite green toxicity at therapeutic dosages.

Formalin removes O2 from the water at a rate of 1 ppm O2 for every 5 ppm formalin used. Thus, supplemental aeration is suggested during treatment with formalin.

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